Publications

The incidence rate of hybridization appears to be much higher for parulid warblers compared to other bird taxa. Over 50% of the species in this family have been reported to hybridize. Here, we report genetic and morphometric analysis of a suspected hybrid of a previously unreported species cross in the genus Oreothlypis, captured in a montane spruce-fir forest in the Adirondack Mountains of New York. We compared sequences of the mitochondrial ND2 and the nuclear Z chromosomal aconitase intron 9 to published warbler sequences to determine parentage, and compared plumage and morphology to museum specimens. ND2 sequence closely matched Orange-crowned Warbler (O. celata), while aconitase matched Nashville Warbler (O. ruficapilla). Because our specimen was a male and was homozygous for ruficapilla alleles at the Z chromosome, we determined the hybridization event occurred at least two generations ago. This suggests hybridization between these species produces viable offspring. Plumage of the warbler was nearly indistinguishable from pure Nashville Warbler specimens. A Principle Components Analysis of morphometric data showed the hybrid to be morphologically intermediate between the two parent species. This hybridization event occurred well outside of Orange-crowned Warblers' breeding distribution, a finding consistent with Hubbs' principle which states that hybridization is more likely when conspecifics are rare or unavailable. Our finding demonstrates the importance of specimen collecting and genetic methods in documenting aspects of natural history that may be cryptic or infrequent in nature.